International Journal of Web Services Research , Vol. 7, No. 2, 20 10 1 A Dependable Infrastructure for Cooperative Web Services Coordination Eduardo Adilio Pelinson Alchieri Department of Automation and Systems Engineering Federal University of Santa Catarina Florianópolis, Brazil alchieri@das.ufsc.br Alysson Neves Bessani Large Scale Informatics Systems Laboratory University of Lisbon, Faculty of Sciences Lisbon, Portugal bessani@di.fc.ul.pt Joni da Silva Fraga Department of Automation and Systems Engineering Federal University of Santa Catarina Florianópolis, Brazil fraga@das.ufsc.br ABSTRACT: A current trend in the web services community is to define coordination mechanisms to execute collaborative tasks involving multiple organizations. Following this tendency, this work presents a dependable (i.e., intrusion-tolerant) infrastructure for cooperative web services coordination that is based on the tuple space coordination model. This infrastructure provides decoupled communication and implements several security mechanisms that allow dependable coordination even in presence of malicious components. This work also investigates the costs related to the use of this infrastructure and possible web service applications that can benefit from it. KEY WORDS: Dependability, Tuple Spaces, Web Services Coordination INTRODUCTION The Web Services technology, an instantiation of the service oriented computing paradigm (Bichier and Lin 2006), is becoming a de facto standard for the development of distributed systems on the Internet. The attractiveness of web services are its interoperability and simplicity, based on technologies widely used in the web, like HTTP and XML. Its attributes have been the motivation for many industrial and academic efforts for developing concepts and models for distributed applications based on the service-oriented paradigm. The service oriented computing - and more specifically Web Services - is a natural evolution of classical concepts such as RPC and technologies like CORBA (Object Management Group, 2002). In the same way of these, web services provided by an organization must be described in an interface that can be understood and invoked by other parts of a distributed system. The main standards for web services, all based on XML, are: SOAP (Simple Object Access Protocol) - protocol for exchange messages among clients and services, which can operate over several